Through various tests and screenings, an expectant mother can get faint clues as to how healthy the pregnancy will be. One such common diagnostic tool is the double marker test in pregnancy, which helps the mother to know many things about the baby in advance without any worries, and it is quite cheap. In general, double marker tests are necessary for pregnancy to exclude any possibility of serious diseases such as Edwards’s syndrome or Down syndrome, which can affect the development of any child.
What is a double marker test?
The double marker test in pregnancy, also known as the maternal serum screening test, is part of a broader screening test called the first-trimester screening test. Instead, it is classified as a predictive test, meaning its results indicate the likelihood of chromosomal abnormalities.
Specifically, this test analyses blood levels of free human beta-chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein A (PAPP-A). In a typical pregnancy, there are 22 pairs of XX chromosomes in female fetuses or 22 pairs of XY chromosomes in male fetuses. A trisomy is a chromosomal abnormality characterized by the presence of extra chromosomes, such as the following:
- Down Syndrome
This shared trisomy is also known as trisomy 21 because there is an extra copy of chromosome 21.
- Trisomy 18 and trisomy 13
An extra copy of chromosome 18 (Edward syndrome) or chromosome 13 (Patau syndrome) are involved in common chromosomal abnormalities. hCG and PAPP-A levels may be higher or lower than “normal” in pregnancies with these chromosomal abnormalities.
However, blood levels alone do not produce their results. Instead, the blood test is used in conjunction with an ultrasound, called a nuchal translucency (NT) scan, which examines the clear tissue on your baby’s neck.
Why is a double marker test performed?
First-trimester double marker screening and NT scan are not required. However, screening (and others such as cell-free DNA testing) is recommended if you are over the age of 35 or have an increased risk of chromosomal problems, such as if certain medical disorders run in your family. It is important to remember that the result only indicates whether there is an increased risk of trisomy. It cannot be definitively determined if your baby has any abnormalities.
Standard Time of double marker test
Your doctor will ask you to make an appointment towards the end of your first trimester or possibly very early in your second trimester. More specifically, you will have blood drawn sometime between 11 and 14 weeks.
Standard results for the double marker test
You receive a low, medium, or high-risk result. Low risk (“negative test”) is considered a “normal” result and means there is a low chance that your baby has chromosomal abnormalities. If your result is within the normal range, further testing is recommended only if there are other indicators (such as family history, age, etc.) or if you would like more information for other reasons.
However, a low-risk result does not always mean that your baby will not have problems. And it is important to note that first-trimester screening only examines markers for Down syndrome, trisomy 13, and trisomy 18, not other conditions.
Abnormal results for the double marker test
If your test shows an intermediate or high risk (“positive detection”) of abnormalities, you may review your result with a genetic counselor for more information. The result can be confirmed by more definitive and sometimes invasive tests such as noninvasive prenatal testing (NIPT), amniocentesis, or chorionic villus sampling.
Although some of these tests pose some risks to your pregnancy, they do provide a definitive result. Because the double marker test is performed early in your pregnancy, the information gives you time to make important decisions about further testing, medical treatment, and the general management of your pregnancy and delivery. Knowing your risk can also help you prepare for the possibility of having a child with special needs and help you find the support you need.
To test or not to test
If you don’t know what to do, first weigh the pros and cons of the double marker test and the first-trimester assessment. Ask yourself how knowing this information could assist you in your decision to continue testing and in the management of your pregnancy. Be sure to discuss the double marker test in pregnancy and its usefulness with your doctor based on your circumstances. Whatever you decide, keep close contact with your doctor because your doctor is the prime key to a healthy pregnancy.
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